This application is based upon and claims priority to Japanese Patent Application No. Heisei 11-243739 filed Aug. 30, 1999, the contents of which are incorporated herein by reference.
Conventionally, refrigeration type and adsorption type dehumidifiers have been used. Also, a dry type dehumidifier having a honey-comb rotor with silica gel fixed thereto has been used in recent years. The dry type dehumidifier with the honey-comb rotor is suitable to provide air having a low dew point, i.e., low absolute humidity. However, dry type dehumidifiers are limited in their ability to produce very dry air for the following reasons. Dry type dehumidifiers using the honey-comb rotor generate adsorption heat when the adsorbent, such as silica gel, adsorbs moisture in the air to be dehumidified. Since the temperature of the air to be dehumidified increases, the relative humidity decreases. However, the dew point (absolute humidity) is still too high. It is difficult to decrease the absolute humidity when the relative humidity is low.
To improve the performance of a dry type dehumidifier using a honey-comb rotor, the air to be dehumidified could be cooled before processing. To avoid this, Japanese Published Application No. Showa 62-68520 proposes using the honey-comb rotor as a sensible heat exchanger with an air stream through the rotor removing adsorption heat so that the honey-comb rotor can dehumidify.
The technology indicated by the above-mentioned reference is related to equipment which adsorbs the moisture in processed air, and cools the honey-comb rotor using an air stream derived from the atmosphere. The system releases adsorption heat to thereby avoid a drop off in the dehumidification.
However, despite the cooling air stream, the temperature of the honey-comb rotor may still increase because of the adsorption heat. Therefore, the system disclosed in Japanese Patent Publication No. 62-68520 may still experience some drop off in the dehumidification ability.
Accordingly, it is an object to the present invention to solve the above problems and avoid any drop off in the dehumidification ability.
These and another objects are accomplished by providing a heat exchanger, perhaps a cross flow heat exchanger, having first and second passages. During dehumidification (adsorption of moisture) in the first passages, water is evaporated from the second passages. This water can be introduced to the second passages during reactivation (desorption of moisture) in the first passages or at another time.
If the water is introduced to the second passages during reactivation, the first and second passages have therein first and second moisture adsorbents. During a first time period, air to be dehumidified is passed through the first passages of the heat exchanger and cooling air is passed through the second passages of the heat exchanger to remove heat generated in the first passages and to desorb moisture adsorbed by the second moisture adsorbent. During a second time period, a heating fluid is passed through the second passages of the heat exchanger to heat the first passages and supply moisture for adsorption to the second moisture adsorbent. Also during the second time period, removal air is passed through the first passages of the heat exchanger to eliminate water adsorbed by the first moisture adsorbent during the first time period.
If water is introduced to the second passages at a time other than during reactivation, it is not necessary for the second passages to have a moisture adsorbent therein. Warm air is passed through the second passages during the second time period to heat the first passages. To supply moisture, a spray device may supply a large amount of misty minute liquid drops to the second passages during the first time.
The first moisture adsorbent in the first passages of the heat exchanger may be a silica gel, an ion exchange resin, or a hydrophilic zeolite. The second moisture adsorbent in the second passages may be a silica gel, an ion exchange resin, a hydrophilic zeolite, or a nonwoven fabric. Alternatively, the second moisture adsorbent may be formed by surface processing on the surfaces of the second passages.
The heating fluid may be warm humid air, and the dehumidifier may have a heating and humidifying device to receive air exiting the second passages of the heat exchanger during the second time period, to heat and humidify the air, and to pass the warm humid air through the second passages of the heat exchanger as the heating fluid.
A plurality of heat exchangers may be arranged in a circular configuration and rotatably supported by a frame so that a first portion of the heat exchangers perform in the first time period while concurrently a second portion of the heat exchangers perform in the second time period.
The dehumidifier may have a heater and a desorption heat exchanger. The heater heats the removal air in the second time period before passing the removal air through the first passages of the heat exchanger. The desorption heat exchanger has first and second passages. The first passages of the desorption heat exchanger receive air exiting the first passages of the heat exchanger during the second time period. Also during the second time period, the second passages of the heat exchanger receive removal air before the removal is heated by the heater.